j p bhandari

Carbon Sequestration Methods to Mitigate Climate Change - 21st Century Engineering Challenge

By: Dr. Sadanand Guhe (sadanandguhe@jnec.ac.in)
Date: 5th Jan 2021

Global warming is increasing due to Greenhouse Gases (GHG) emissions. GHGs include carbon dioxide (76%), methane and other gases which are the cause of climate change and are not good for an environment. If we want to control GHGs emission then the Government of India must decide on reducing carbon dioxide per unit of Gross Domestic Product (GDP) by 35% until the year 2030, compared to its level in the year 2015.

At the same time all countries must take measures to curb GHG emissions, sooner the better; otherwise more burdens will be to do so in later years. Just to remind you that India is the world’s third largest GHGs emitter in line with China and USA. As per the recent report published by Global Coal Plant Tracker, India has 221 Gigawatts (GW) of operating coal plants which is the world’s third largest fleet with 11% of global capacity. Another 36GW is being built and a further 58GW is at earlier stages of development. India being world’s second largest coal consumer after China and having moved ahead of the US in 2015 in terms of consumption, recent report by the Potsdam Institute for Climate Impact Research quotes that India released 3,571 M tonnes of carbon dioxide equivalent (MtCO2e) in the same year. For electricity generation, India largely depends on thermal power plants which emit GHGs, predominantly carbon dioxide and carbon monoxide, leaving heavy carbon footprints and climate change. If proper pollution control measures are not taken, coal based thermal power plants put health risks to humans and environment due to release of carbon dioxide, carbon monoxide and other hazardous gases in the air. As per a recent report published by the Lancet Planetary Health, one in every eight deaths in India is due to air pollution. Moreover, heavy industrialization and excessive use of fossil fuels and burning of biomass in rural areas are resulting in more of these gases being released into the atmosphere. At the same time it is to be noted that due to COVID-19 pandemic situation in the year 2020 and subsequent lockdown, carbon dioxide emissions have drastically reduced, but lockdowns must not be mistaken as the solution to this problem.

indias co2 emmision
Geological Survey

So after understanding the effects of carbon emissions, question arises how to curb these emissions primarily from thermal power plants and other heavy industries such as cement, steel and refineries? Well, banning deforestation, encouraging tree plantation, reducing burning of fossil fuels etc. will give positive result after some time in future. Hence for an immediate effect to reduce or eliminate this detrimental effect, carbon present in the earth’s atmosphere as carbon dioxide or carbon monoxide can be trapped or converted by carbon sequestration methods. Carbon sequestration or capture technology needs to be refined and implemented to control these emissions. In this method carbon dioxide present in the atmosphere or emitted from industries is separated and trapped or deposited in a reservoir deep in the earth. Alternatively carbon dioxide or methane can be converted to valuable products instead of releasing it into the atmosphere. Carbon sequestration can be classified into two approaches, namely Natural which is more into using biological processes to improve management of forestation, wetland, soils quality through regenerative agriculture which is about capturing carbon from the air and releasing it into the soil as an organic carbon etc.

However technological approach is more into technology enabled removal of carbon or carbon dioxide from the air, flue gases from Industries and exhaust gases from automobiles. Moreover natural carbon-removal processes can also be improved using technology approach to increase carbon sequester. In a natural approach continuous soil testing needs to be done to analyze nitrogen requirement of soil and subsequently be supplied in a controlled manner to convert carbon in soil to microbial organic matter. Also implementing regenerative agriculture, which is a method wherein farmers opt to not plow soils so that carbon is not released and sow seeds by drilling it into the soil. Also plants called cover crops can be grown to cover the soil after harvesting the main crop. Other ways include planting three or more crops in rotations over several seasons coupled with grazing by livestock. Sometimes reduced use of fertilizer and pesticide is also considered as regenerative agriculture. All these measures taken collectively or independently improve carbon sequestration in the soil. Talking about technological approach, it is necessary to point out that many available technologies to sequester or capture carbon dioxide are at demonstration level. In carbon sequestration or carbon capture, carbon dioxide present in the atmosphere or emitted from industries is chemically or physically removed.

In chemical methods carbon dioxide is converted to valuable material instead of releasing it into the atmosphere whereas in physical method carbon dioxide is trapped or deposited in a reservoir, called geologic sequestration. Some companies are working on separating it from air and dumping it deep into Earth, some are working on thermal power generation process which will have zero discharge of carbon into the atmosphere e.g. process called ‘Allam Cycle’ converts gaseous fuels into thermal energy, but importantly captures carbon dioxide and water in the process. Another latest example is of BS-VI emission standard norms compliant vehicles, made mandatory by Government of India are installed on the exhaust of an automobile. It is basically a catalytic converter which captures carbon present in an exhaust gases and releases less polluted gases into the atmosphere. Other processes include enhanced oil recovery from oil fields where carbon dioxide is pumped in oil well from one end which pushes oil out from other end. Once oil recovered, these wells are then plugged trapping carbon dioxide deep underground in these wells. Carbon mineralization process captures carbon dioxide from the air and stores it in the form of permanent carbonate minerals, such as calcite or magnesite. Carbon dioxide can be used to obtain value added products ranging from carbonating beverages, plastics, concrete additives, supplying to plants in greenhouses, or converting it into methane or methanol to paints, adhesives, olefins, syngas and chemicals.

New technologies are being discovered and researchers are working tirelessly to provide better solutions. In order to prevent further damage to the environment, every country should reach negative carbon emissions i.e. removing more carbon from air than putting in to the atmosphere. Combination of measures can be taken to tackle this problem faster i.e. increase natural carbon-removal approaches and investing in technological approaches through research and development. As per United Nations Emissions Report published in the year 2017, world needs to sequester and store 8 Gigatonnes of carbon dioxide annually on an average by the year 2050. Not to forget that it is also a responsibility of the major economies of the world, or so called developed countries, to transfer the needed carbon sequestration technology and methods to developing and poor countries to help them cut emissions and adapt to carbon capture and sequestration. All efforts ultimately help in mitigation of climate change and chemical engineers have major role to play in saving mother earth! Chemical Engineering department of MGM University is also committed to address this problem through research on carbon capture. I have, in collaboration with research group from the National Environmental Engineering and Research Institute (NEERI-CSIR) Nagpur, worked on chemical looping combustion technology to provide carbon sequestration solutions mainly for thermal power plant’s exhaust gases. Although we have obtained promising results but further investigations are to be done.